Abstract: In order to study the surface integrity of superalloy GH4169 under high-speed milling, the rules governing the cutting surface morphology and microstructure of the superalloy are analyzed on the basis of the measurments of the variation of milling forces with the changes of the processing parameters and time during high-speed milling. The results indicate that in the range of the experimental parameters, the forces have a trend of first rising and then falling, and that they reach the peak when the cutting speed of end milling is 75.4 m/min. The surface roughness decreases with increasing cutting speed, but increases with increasing feed. Under the conditions of the experiment, a metamorphic layer appears at the milling surface generated by the major cutting edge, but the layer is hardly observed at the surface generated by vice cutting edge. The thickness of the metamorphic layer changes as the contact angle changes, and the thickest metamorphic layer is observed where the contact angle is about 120°. The thickness of the metamorphic layer has a trend of first rise and then fall as the cutting speed increases. The thickest metamorphic layer of end milling appears when the cutting speed is about 75.4 m/min, which is about 150.7 m/min of side milling. It is suggested that the thrust force plays the main mechanical role of forming the metamorphic layer, and that the coupled thermo-mechanical action during high-speed milling is the basic cause that generates the metamorphic layer.

Key words: superalloys, high-speed milling, surface microstructure, surface integrity, surface morphology